| /* |
| * Detect Soft Lockups |
| * |
| * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc. |
| * |
| * this code detects soft lockups: incidents in where on a CPU |
| * the kernel does not reschedule for 10 seconds or more. |
| */ |
| #include <linux/mm.h> |
| #include <linux/cpu.h> |
| #include <linux/nmi.h> |
| #include <linux/init.h> |
| #include <linux/delay.h> |
| #include <linux/freezer.h> |
| #include <linux/kthread.h> |
| #include <linux/lockdep.h> |
| #include <linux/notifier.h> |
| #include <linux/module.h> |
| #include <linux/sysctl.h> |
| |
| #include <asm/irq_regs.h> |
| |
| static DEFINE_SPINLOCK(print_lock); |
| |
| static DEFINE_PER_CPU(unsigned long, softlockup_touch_ts); /* touch timestamp */ |
| static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */ |
| static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); |
| static DEFINE_PER_CPU(bool, softlock_touch_sync); |
| |
| static int __read_mostly did_panic; |
| int __read_mostly softlockup_thresh = 60; |
| |
| /* |
| * Should we panic (and reboot, if panic_timeout= is set) when a |
| * soft-lockup occurs: |
| */ |
| unsigned int __read_mostly softlockup_panic = |
| CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; |
| |
| static int __init softlockup_panic_setup(char *str) |
| { |
| softlockup_panic = simple_strtoul(str, NULL, 0); |
| |
| return 1; |
| } |
| __setup("softlockup_panic=", softlockup_panic_setup); |
| |
| static int |
| softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) |
| { |
| did_panic = 1; |
| |
| return NOTIFY_DONE; |
| } |
| |
| static struct notifier_block panic_block = { |
| .notifier_call = softlock_panic, |
| }; |
| |
| /* |
| * Returns seconds, approximately. We don't need nanosecond |
| * resolution, and we don't need to waste time with a big divide when |
| * 2^30ns == 1.074s. |
| */ |
| static unsigned long get_timestamp(int this_cpu) |
| { |
| return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ |
| } |
| |
| static void __touch_softlockup_watchdog(void) |
| { |
| int this_cpu = raw_smp_processor_id(); |
| |
| __raw_get_cpu_var(softlockup_touch_ts) = get_timestamp(this_cpu); |
| } |
| |
| void touch_softlockup_watchdog(void) |
| { |
| __raw_get_cpu_var(softlockup_touch_ts) = 0; |
| } |
| EXPORT_SYMBOL(touch_softlockup_watchdog); |
| |
| void touch_softlockup_watchdog_sync(void) |
| { |
| __raw_get_cpu_var(softlock_touch_sync) = true; |
| __raw_get_cpu_var(softlockup_touch_ts) = 0; |
| } |
| |
| void touch_all_softlockup_watchdogs(void) |
| { |
| int cpu; |
| |
| /* Cause each CPU to re-update its timestamp rather than complain */ |
| for_each_online_cpu(cpu) |
| per_cpu(softlockup_touch_ts, cpu) = 0; |
| } |
| EXPORT_SYMBOL(touch_all_softlockup_watchdogs); |
| |
| int proc_dosoftlockup_thresh(struct ctl_table *table, int write, |
| void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| touch_all_softlockup_watchdogs(); |
| return proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| } |
| |
| /* |
| * This callback runs from the timer interrupt, and checks |
| * whether the watchdog thread has hung or not: |
| */ |
| void softlockup_tick(void) |
| { |
| int this_cpu = smp_processor_id(); |
| unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu); |
| unsigned long print_ts; |
| struct pt_regs *regs = get_irq_regs(); |
| unsigned long now; |
| |
| /* Is detection switched off? */ |
| if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) { |
| /* Be sure we don't false trigger if switched back on */ |
| if (touch_ts) |
| per_cpu(softlockup_touch_ts, this_cpu) = 0; |
| return; |
| } |
| |
| if (touch_ts == 0) { |
| if (unlikely(per_cpu(softlock_touch_sync, this_cpu))) { |
| /* |
| * If the time stamp was touched atomically |
| * make sure the scheduler tick is up to date. |
| */ |
| per_cpu(softlock_touch_sync, this_cpu) = false; |
| sched_clock_tick(); |
| } |
| __touch_softlockup_watchdog(); |
| return; |
| } |
| |
| print_ts = per_cpu(softlockup_print_ts, this_cpu); |
| |
| /* report at most once a second */ |
| if (print_ts == touch_ts || did_panic) |
| return; |
| |
| /* do not print during early bootup: */ |
| if (unlikely(system_state != SYSTEM_RUNNING)) { |
| __touch_softlockup_watchdog(); |
| return; |
| } |
| |
| now = get_timestamp(this_cpu); |
| |
| /* |
| * Wake up the high-prio watchdog task twice per |
| * threshold timespan. |
| */ |
| if (time_after(now - softlockup_thresh/2, touch_ts)) |
| wake_up_process(per_cpu(softlockup_watchdog, this_cpu)); |
| |
| /* Warn about unreasonable delays: */ |
| if (time_before_eq(now - softlockup_thresh, touch_ts)) |
| return; |
| |
| per_cpu(softlockup_print_ts, this_cpu) = touch_ts; |
| |
| spin_lock(&print_lock); |
| printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", |
| this_cpu, now - touch_ts, |
| current->comm, task_pid_nr(current)); |
| print_modules(); |
| print_irqtrace_events(current); |
| if (regs) |
| show_regs(regs); |
| else |
| dump_stack(); |
| spin_unlock(&print_lock); |
| |
| if (softlockup_panic) |
| panic("softlockup: hung tasks"); |
| } |
| |
| /* |
| * The watchdog thread - runs every second and touches the timestamp. |
| */ |
| static int watchdog(void *__bind_cpu) |
| { |
| struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
| |
| sched_setscheduler(current, SCHED_FIFO, ¶m); |
| |
| /* initialize timestamp */ |
| __touch_softlockup_watchdog(); |
| |
| set_current_state(TASK_INTERRUPTIBLE); |
| /* |
| * Run briefly once per second to reset the softlockup timestamp. |
| * If this gets delayed for more than 60 seconds then the |
| * debug-printout triggers in softlockup_tick(). |
| */ |
| while (!kthread_should_stop()) { |
| __touch_softlockup_watchdog(); |
| schedule(); |
| |
| if (kthread_should_stop()) |
| break; |
| |
| set_current_state(TASK_INTERRUPTIBLE); |
| } |
| __set_current_state(TASK_RUNNING); |
| |
| return 0; |
| } |
| |
| /* |
| * Create/destroy watchdog threads as CPUs come and go: |
| */ |
| static int __cpuinit |
| cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
| { |
| int hotcpu = (unsigned long)hcpu; |
| struct task_struct *p; |
| |
| switch (action) { |
| case CPU_UP_PREPARE: |
| case CPU_UP_PREPARE_FROZEN: |
| BUG_ON(per_cpu(softlockup_watchdog, hotcpu)); |
| p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); |
| if (IS_ERR(p)) { |
| printk(KERN_ERR "watchdog for %i failed\n", hotcpu); |
| return NOTIFY_BAD; |
| } |
| per_cpu(softlockup_touch_ts, hotcpu) = 0; |
| per_cpu(softlockup_watchdog, hotcpu) = p; |
| kthread_bind(p, hotcpu); |
| break; |
| case CPU_ONLINE: |
| case CPU_ONLINE_FROZEN: |
| wake_up_process(per_cpu(softlockup_watchdog, hotcpu)); |
| break; |
| #ifdef CONFIG_HOTPLUG_CPU |
| case CPU_UP_CANCELED: |
| case CPU_UP_CANCELED_FROZEN: |
| if (!per_cpu(softlockup_watchdog, hotcpu)) |
| break; |
| /* Unbind so it can run. Fall thru. */ |
| kthread_bind(per_cpu(softlockup_watchdog, hotcpu), |
| cpumask_any(cpu_online_mask)); |
| case CPU_DEAD: |
| case CPU_DEAD_FROZEN: |
| p = per_cpu(softlockup_watchdog, hotcpu); |
| per_cpu(softlockup_watchdog, hotcpu) = NULL; |
| kthread_stop(p); |
| break; |
| #endif /* CONFIG_HOTPLUG_CPU */ |
| } |
| return NOTIFY_OK; |
| } |
| |
| static struct notifier_block __cpuinitdata cpu_nfb = { |
| .notifier_call = cpu_callback |
| }; |
| |
| static int __initdata nosoftlockup; |
| |
| static int __init nosoftlockup_setup(char *str) |
| { |
| nosoftlockup = 1; |
| return 1; |
| } |
| __setup("nosoftlockup", nosoftlockup_setup); |
| |
| static int __init spawn_softlockup_task(void) |
| { |
| void *cpu = (void *)(long)smp_processor_id(); |
| int err; |
| |
| if (nosoftlockup) |
| return 0; |
| |
| err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
| if (err == NOTIFY_BAD) { |
| BUG(); |
| return 1; |
| } |
| cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
| register_cpu_notifier(&cpu_nfb); |
| |
| atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
| |
| return 0; |
| } |
| early_initcall(spawn_softlockup_task); |